The history of the NHS is also a history of economic migration. Practically from its conception, the health service suffered acute shortages of staff, and that shortfall was met then, as it is now, by "importing" nurses, doctors and auxiliary staff from overseas. Archive pictures of the birth of the health service show an almost uniformly white-skinned workforce, although many of those nurses would be Irish-born. Within a few years, the ethnic mix of the NHS was radically more diverse, especially in cities, and in the so-called "Cinderella" specialities such as mental health and geriatric care.

The Caribbean was a primary source of nurses. As early as 1949, the health and labour ministries launched recruitment campaigns that resulted in thousands of nurses arriving in Britain and being dispersed to hospitals all over the UK. Nurses also came from Malaysia, Mauritius and other parts of the empire.

Immigrant Irish nurses were already well-established in hospitals prior to the establishment of the NHS; more came, post-1948, attracted by the superior pay and prospects on offer in the UK. It was estimated that by 1971, 12% of Britain's nurses were Irish nationals.

Doctors from India and Pakistan came in huge numbers in response to an appeal in the early 1960s by the then health minister Enoch Powell. More than 18,000 subsequently arrived in the UK, underpinning healthcare provision in many areas. It was reported in 2003 that in the Rhondda valley, in Wales, 73% of GPs were south Asian.

In recent years the NHS has widened its catchment area for health workers. Beween 2002-03 and 2006-07, more than 14,000 nurses from the Phillipines registered with the UK nursing and midwifery council. India was the second biggest exporter of nurses to the UK, with more than 10,000 nurses registering over this period. Thousands more came from Australia, South Africa, Nigeria, New Zealand, Pakistan, Ghana and Zimbabwe. In 2006-07 Poland was the biggest single European economic area supplier of registered nurses to the NHS.

Recent years have seen doctors from Germany and France and other EU countries working in the UK, often on a locum basis providing GP out of hours services, or as surgeons carrying out routine NHS operations for private healthcare-owned independent treatment centres.

The latest figures from the General Medical Council show that just over 91,000 of the UK's 243,910 registered doctors earned their medical qualification outside Britain, most of them (68,836) outside the European economic area. India was the country of origin of 27,809 of these doctors, South Africa accounting for 7,775 and Pakistan 7,306.

Refugee and asylum seeker doctors account for a tiny - if underused - part of the NHS medical workforce. The British Medical Association holds details of 1,199 refugee and asylum-seeking doctors in the UK. Of these, 172 are working in the NHS, although nearly one in five of the 1,027 who are not currently working in the NHS are "job-ready", having obtained the professional and linguistic exams needed to work here.